The goal of our research program is to achieve an increased understanding of the range of structural diversity in the immune system. In line with this general objective, we are carrying out the following projects. 1. Structure and function of immunoglobulin variants. We wish to continue studies of the crystallizable human IgGl myeloma protein, Dob. We plan to complete the analysis of its primary structure, and to investigate the effects of the known structural abnormality (hinge region deletion) on its biological activity, in particular, on its ability to activate the complement system. 2. Studies on the structure of mouse lambda light chains. Our objectives are to determine the amino acid sequence of the variable regions of mouse lambda 2 chains and to establish the sequence of both the variable and constant regions of a group of recently discovered lambda variants (designed lambda 3). Long-term goals are to determine the primary structures of these proteins, to identify the genes that code for them, and to obtain insight into the regulation of gene expression in this system. This project is a collaboration with the laboratory of Dr. H.N. Eisen. 3. Studies on the immune and complement systems of lower vertebrates. We wish to determine major structural features of the various immunoglobulins in the bullfrog, Rana catesbeiana, especially to determine similarities and differences from mammalian immunoglobulins. We also plan to isolate and partially characterize the first complement component, Clq, in this species and in certain other lower vertebrates.